add rustdoc comments with examples for the string versions of to_base64 and from_base64
rustpkg: Factor out tests; use a condition instead of returning an option

Pulled out tests into their own modules inside the files they test,
as per the draft style guidelines.

Started a new module, path_util, for utility functions to do with
paths and directories.

Changed default_dest_dir to use a condition and return Path
instead of Option<Path>.
Add comments for the implementations of from_base64 and to_base64 for .
move rustdoc comments so that they attach to the functions rather than the impl blocks.
Doc review, as requested :-).

Mostly just phrasing things differently, which is a matter of taste. Feel free to use or not use any of the changes I'm suggesting.

I would say this one thing should be changed, though, not necessarily the way I changed it here.

     * Convert any string (literal, `@`, `&`, `~`)
     * that contains a base64 encoded value, to the byte values it encodes.

If this structure is going to be used, either the entire clause, 'that contains a base64 encoded value', should be bracketed by commas, or the comma at the end of the clause should be removed.
Merge pull request #1 from danluu/silly_style_changes

Doc review, as requested :-).
Add a lint mode for unused unsafe blocks/functions
core: remove unnecessary unsafe blocks/functions
std: remove unused unsafe blocks/functions
rustc: remove unnecessary unsafe blocks/methods
syntax: remove unnecessary unsafe blocks/functions
test: remove unnecessary unsafe blocks/functions
update copyright notice on base64.rs
Change to 4-space indents in code examples
core::rt: Restructure task_from_last_cleanup_job to borrow correctly

We need a number of mutable references to contexts so name it
`get_contexts` and return a tuple of all of them.
core::rt: Rename block_running_task_and_then to deschedul_...
core::rt: Insert calls to run_cleanup_tasks after all context switches
core::rt: Schedulers only need a single cleanup_job at a time

Each context switch has up to one cleanup job and it is always
executed immediately after the context switch.
core::rt: All context switches are followed by a cleanup action
core::rt: Clean up the thread-local scheduler code

Remove the ThreadLocalScheduler type in favor of functions.
Move everything into the sched::local module.